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Early categorization of Particles

Early categorization of Particles. Early collider experiments started to reveal more and more particles, and people started to question whether they were truly “Fundamental”, but did allow for the prediction of “missing particles that were later found.

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Early categorization of Particles

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  1. Early categorization of Particles Early collider experiments started to reveal more and more particles, and people started to question whether they were truly “Fundamental”, but did allow for the prediction of “missing particles that were later found. Attempts to rationalize this “zoo” of particles led Gell-Mann (and independently Zweig) to suggest more fundamental building blocks (based largely on the observation of patterns [symmetries] in the properties of the particles; they appeared in families of 1, 8, 10, 27 etc. members]:

  2. The Standard Model http://newsimg.bbc.co.uk/media/images/41136000/gif/_41136526_standard_model2_416.gif

  3. http://www.pha.jhu.edu/~dfehling/particle.gif

  4. Strong Force: Confinement T-R fig. 14-13. The strong force is sometimes discussed in terms of a rubber band that gets stronger as it gets stretched more, eventually the band (or “flux tube”) possess enough energy to create a new quark-antiquark pair and the initial interaction disappears. As a result of this, longer range interaction among quarks can be viewed as meson exchange

  5. The Standard Model BARYONS Proton: duu Neutron ddu W- sss MESONS: Pion p- ubar-d See the website for the third generation and more details http://en.wikipedia.org/wiki/Standard_Model

  6. Detecting Radiation • Ion Chambers Geiger counters proportional counters: Large positive voltage on thin wire leads to ionization amplification near that wire. Charge collected is proportional to energy deposited in the gas, if the voltage is not too high, and all or nothing if the voltage is above this threshold. For small biases, there is insufficient energy to produce secondary ionization near the collector, this is then an ion chamber. Gas filled volume with a biased wire or wires in the middle somewhere

  7. Detecting Radiation • Sintilators: Radiation creates many electron-hole pairs and these recombine at doping sites to give off particular wavelengths of visible photons, number is proportional to energy. The light is typically detected by a Photo-Multiplier Tube (PMT). This is a very crude schematic of a PMT, in reality the dynodes are put in a focusing arrangement, there are 11 to 14 of them, and most often the photo-cathode is on the end. http://www.files.chem.vt.edu/chem-ed/optics/detector/pmt.html

  8. Detecting Radiation • Cerenkov Detectors: When charged particles travel through an insulator with speed greater than c/n they emit light in a kind of shock wave, and this is detected by PMT’s http://forum.prisonplanet.com/index.php?topic=78431.0

  9. Detecting Radiation • Semiconductor Detectors: As with a scintilator, e-h pairs are created as the charged particle goes through the medium, but here, the medium is a reverse biase p/N junction (possibly with a big intrinsic region in the middle) and the charges are collected directly by a preamplifier connected to the medium. These tend to have greater resolution than scintilators (more e-h pairs than photo-electrons in the PMT).

  10. Fundamental forces as particle exchange T-R fig. 14-13. The strong force is sometimes discussed in terms of a rubber band that gets stronger as it gets stretched more, eventually the band (or “flux tube”) possess enough energy to create a new quark-antiquark pair and the initial interaction disappears.

  11. Events at LHC(6 Dec. 2009) Event captured by the inner trackers (straw-tube section built here in Swain Hall!)

  12. Beyond the Standard Model • SM does not account for the following: • Gravity (4): current field theories do not easily meld with General relativity • Matter/Antimatter asymmetry of the universe (14) • Neutrino mass/oscillations (14) • Solar Neutrino problem (5) • Dark Matter • Dark Energy • Does not make specific predictions on mass (lots of free parameters). • “hierarchy problem” (Weak scale << Planck scale)

  13. Three neutrino flavors: That’s it!* *Looking at the lifetime (line width) of the Z boson has put strong limits on the number of neutrino families that participate in physics we understand hep.ps.uci.edu/quarknet/lectures/LectureCasper.ppt

  14. Solar Neutrino Problem http://en.wikipedia.org/wiki/Neutrino

  15. Connections between HEP and Astrophysics SNO http://www.snolab.ca/public/science/index.html A typical example of a HEP astrophysical observatory: located 2 km underground!

  16. Connections between HEP and Astrophysics SNO SNO could see three different types of neutrino interactions and this allowed them to demonstrate that some neutrinos from the SUN changed flavor before reaching the detector. SNO collaboration PRL 87 071301 (2001) http://www.snolab.ca/public/science/index.html

  17. Cosmology:The Expanding Universe Hubble’s original data (out to 2Mpc) http://www.astro.rug.nl/~hidding/ao/ao.html COSMOLOGICAL PRINCIPLE: “The universe looks roughly the same (isotropic and Homogeneous) to all observers.” http://atropos.as.arizona.edu/aiz/teaching/nats102/lecture22.html

  18. Cosmology:The Expanding Universe http://www.cfa.harvard.edu/~huchra/hubble/ The Hubble constant as a function of time; The primary changes have come from improvement in the “standard candle” used to determine distance. Initially Cepheid variables (that turned out to be clusters), now we use type 1a supernovae. Latest values: 74.2(3.6) (Hubble); 73.5(3.2) WMAP ; overall “best value” 70.8(1.6) kps/Mpc => the age of the Universe is about 13.7 Gyr

  19. Evolution of Temperature with Time for the Big Bang

  20. P301 Lecture 8“CMB fit to BB spectrum” • The plot on the right shows data from the FIRAS instrument on the original COBE satellite experiment. The measurement of interest here was the set of residuals (i.e. the lower plot of the differences between the measured spectrum and that of a true black body) • The curves correspond to various non-ideal BB spectra: • 100 ppm reflector (e) • 60 ppm of extra hot electrons adding extra 60ppm of energy just about 1000 yrs after the big bang (m before, y after this time) http://www.astro.ucla.edu/~wright/CMB.html

  21. More details in the CMB Color scale 0-4K 2.721-2.729K +/-100 mK range http://map.gsfc.nasa.gov/universe/WMAP_Universe.pdf

  22. Big Bang Nucleosynthesis http://atropos.as.arizona.edu/aiz/teaching/nats102/lecture22.html This puts strong limits on the overall density of normal “Baryonic” matter in the Universe.

  23. Cosmic Microwave Background http://www.pas.rochester.edu/~afrank/A105/LectureXVI/COBE_Wmap.jpg

  24. Cosmic Microwave Background WMAP satellite data: See also : http://map.gsfc.nasa.gov/

  25. Cosmic Microwave Background http://www.cobankopegi.com/b/wmap.jpg

  26. Office Hours Next week • Monday 2:00 to 3:00 • Tuesday 1:00 to 3:30 • Wednesday 8:45 to 9:45 • Contact me if you need to meet at some time other than that and we should be able to arrange something.

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